Across America’s southwest deserts are small isolated springs (like oases) that sometimes support unique species of fish called pupfishes. Essentially an entire species of pupfish may be found in a spring that may be as small as a bathtub, to as large as a swimming pool. The extremely limited distributions and small population sizes place each species under the Federal Endangered Species Act. This means that the Federal Government does what it can to protect these really interesting species. Department chair Murray Itzkowitz has spent the last ten years re-claiming the habitat of the pupfish in the West Texas desert.

Spawning Cyprinodon bovinus in the West Texas desert. Note the Pecos gambusia waiting to attack the female's released eggs.

When it is cold, we first cut the bulrush weeds
before the digging begins.

We then remove the roots and the mud, an extremely difficult and tedious operation.

I began studying one of these endangered species, Leon Springs pupfish (Cyprinodon bovinus), near Ft. Stockton, Texas. At the time, my aim was to use them to test general hypotheses about social behavior. However, in 2003, I noticed a decline in the population. I immediately called the Texas Nature Conservancy (they owned the property) and the Federal Fish and Wildlife Service. They took notice in 2005 when I pointed out that the once robust population was now down to maybe 10 individuals. They suggested that I apply for funding from the Texas Parks and Wildlife Department (TPWD) and do what I could to halt the likely extinction.

I thought the demise of the pupfish was caused by two interrelated factors. First, the shoreline that the pupfish used for reproduction was being encroached by bulrush weeds. I really don’t know why this was happening but it was clear that these weeds were converting shallow breeding habitat into land!

Second, the reduction in shallow areas also caused increased predation of pupfish eggs by another endangered fish, the Pecos gambusia (Gambusia Nobilis). I speculated that the loss of habitat modified the micro distribution of the Pecos gambusia making them more likely to eat the pupfish’s eggs. While habitat loss has been linked to the decline in many species, this appears to be the first record of one endangered species threatening the extinction of another one.

Clearly I could never get permission to eliminate one endangered species to protect another one.

With funding from the Texas Parks and Wildlife Department, we expanded the shallow areas and documented the reproduction of the pupfish and their interactions with the gambusia. It was a slow process but over the next several years, the gambusia did interact less with the pupfish and gradually the pupfish population increased. After 7 years, the pupfish population now is sufficiently robust to make extinction unlikely in the absence of any serious environmental perturbation.

Of course, serious environmental disturbances in the southwest are not unusual. With an additional grant from the TPWD, we are now expanding the pupfish habitat to nearby localities where this pupfish has gone extinct. Because there still are not enough fish in the rejuvenated spring to share with other habitats, we will reintroduce this pupfish from a captive population maintained for nearly 30 years in a federal fish hatchery in New Mexico.

Reintroducing highly endangered species into their former habitat has always been controversial because often the habitat has changed, making it unlikely that it will support the species. More recently, conservationists also have come to realize that captivity sometimes causes species to “evolve” in ways that make them unsuitable to survive in appropriate habitat. For this reason we will be examining the genotype and phenotypes of the captive population relative to the current wild population and observe how they adjust and hopefully survive in their new habitat.

We then add cement steps to provide the pupfish with suitable spawning surfaces and to stop the bulrush from returning.

Two current graduate students, Andrew Black and Kimberly Little, are observing the pupfish in the renovated shallow area in the summer .... when the temperature is about 105˚F.